Various embodiments described herein relate to light emitting devices and assemblies and methods of manufacturing the same, and more particularly, to Light Emitting Diodes (LEDs), assemblies thereof and fabrication methods therefor.
LEDs are widely known solid-state lighting elements that are capable of generating light upon application of voltage thereto. LEDs generally include a diode region having first and second opposing faces, and include therein an n-type layer, a p-type layer and a p-n junction. An anode contact ohmically contacts the p-type layer and a cathode contact ohmically contacts the n-type layer. The diode region may be epitaxially formed on a substrate, such as a sapphire, silicon, silicon carbide, gallium arsenide, gallium nitride, etc., growth substrate, but the completed device may not include a substrate. The diode region may be fabricated, for example, from silicon carbide, gallium nitride, gallium phosphide, aluminum nitride and/or gallium arsenide-based materials and/or from organic semiconductor-based materials. Finally, the light radiated by the LED may be in the visible or ultraviolet (UV) regions, and the LED may incorporate wavelength conversion material such as phosphor.
An LED component provides a packaged LED die for mounting on a board, such as a Metal Core Printed Circuit Board (MCPCB), flexible circuit board and/or other printed circuit board, along with other electronic components, for example using surface mount technology. An LED component generally includes an LED die, a submount and other packaging elements.
Submounts are generally used in LED components to interpose an LED die and a printed circuit board. The submount may change the contact configuration of the LED die to be compatible with the pads of the printed circuit board. The submount may also be used to support a phosphor layer and/or an encapsulating dome that surrounds the LED die. The submount may also provide other functionality. Thus, a submount may include a receiving element onto which an LED die is mounted using conventional die-attach techniques, to interface the LED die and a printed circuit board. A submount generally has a thickness of at least 100 μm, and in some embodiments at least 150 μm, and in other embodiments at least 200 μm, and generally includes traces (such as on ceramic panels) and/or leads (such as in Plastic Leaded Chip Carrier (PLCC) package).
Wire bonding is often used to connect the anode contact and/or the cathode contact of an LED die to a submount. Wire bonding is widely used in the microelectronic fabrication industry, and provides a cost effective and flexible interconnect technology. Bond wires may comprise aluminum, copper, silver and/or gold. Wire bond attachment techniques may include ball bonding, wedge bonding and/or compliant bonding. In ball bonding and wedge bonding, the wire is attached at both ends using some combination of heat, pressure and ultrasonic energy to make a weld. In compliant bonding, heat and pressure is transmitted through a compliant or indentable aluminum tape.
LEDs are increasingly being used in lighting/illumination applications, with a goal being to provide a replacement for the ubiquitous incandescent light bulb.